Agar Instructions
How to Use Sierra High Mushrooms Agar Premix
Our High Contrast Agar Premix is designed to make preparing nutrient agar simple and consistent. Just measure the premix, add water, sterilize, and pour.
Mixing Ratio
Use:
20 g Agar Premix per 500 mL of water
The full 100 g pouch can be used to prepare:
100 g Agar Premix + 2.5 liters of water
Common Batch Sizes
Agar PremixWater10 g250 mL20 g500 mL40 g1 liter60 g1.5 liters80 g2 liters100 g2.5 liters
One 500 mL batch will typically make approximately 16 to 20 standard 90 mm agar plates, depending on how much agar is poured into each plate.
The full 100 g pouch can make approximately 80 to 100 agar plates, depending on pour thickness and container size.
What You Will Need
- Sierra High Mushrooms Agar Premix
- Distilled or filtered water
- Digital scale
- Heat-resistant media bottle or flask
- Pressure cooker or autoclave
- Sterile agar plates or suitable containers
- Clean gloves
- Isopropyl alcohol
- Clean pouring workspace
Step 1: Measure the Premix
Use a digital scale to measure the amount of Agar Premix needed for your batch.
For a standard batch, measure:
20 g Agar Premix
Step 2: Add Water
Add the measured premix to:
500 mL of distilled or filtered water
Leave enough empty space in the bottle for the liquid to expand during sterilization.
Do not completely fill the bottle.
Step 3: Mix Thoroughly
Swirl or stir the mixture until the powder is evenly distributed.
Some small particles or cloudiness may remain before sterilization. This is normal.
Do not tightly seal the bottle.
Loosen the cap slightly so pressure can safely escape during sterilization. The cap should be secure enough to stay in place but not fully tightened.
Step 4: Sterilize
Place the bottle in a pressure cooker or autoclave.
Sterilize at:
15 PSI for approximately 20 to 30 minutes
Begin timing once the pressure cooker has reached full operating pressure.
Always follow the safety and operating instructions provided by the manufacturer of your pressure cooker or autoclave.
Do not attempt to open the pressure cooker until it has completely depressurized.
Step 5: Allow the Agar to Cool
Carefully remove the bottle after the pressure cooker has fully depressurized.
Allow the agar to cool before pouring.
A good pouring temperature is approximately:
120°F to 130°F
The bottle should still feel hot, but it should be cool enough to handle safely with heat-resistant gloves.
Pouring while the agar is extremely hot can create excess condensation inside the plates.
Do not wait too long. Agar will begin to thicken and solidify as it cools.
Step 6: Prepare Your Workspace
Pour the agar in the cleanest environment available.
For best results, use:
- A laminar flow hood
- A still-air box
- A thoroughly cleaned and sanitized workspace
Clean your work surface with isopropyl alcohol and allow it to dry.
Wash your hands and wear clean gloves.
Keep agar plates covered as much as possible during pouring.
Step 7: Pour the Plates
Pour a thin, even layer of agar into each sterile plate.
For standard 90 mm plates, approximately 20 to 25 mL per plate is usually sufficient.
Replace the lid immediately after pouring.
Avoid moving or disturbing the plates while the agar is setting.
Step 8: Allow the Plates to Set
Allow the poured plates to cool and solidify at room temperature.
The agar should become firm once fully cooled.
Do not inoculate the plates until the agar has completely set.
Step 9: Check for Contamination
For additional quality control, allow the sealed plates to sit for several days before use.
Inspect the plates for:
- Unexpected growth
- Unusual colors
- Fuzzy patches
- Bacterial spots
- Excess liquid
- Cracked or damaged agar
Discard any plate showing signs of contamination.
Storage
Dry Agar Premix
Store the unopened premix in a cool, dry location away from direct sunlight, moisture, and excessive heat.
Reseal the pouch tightly after opening.
For best results, use a clean, dry utensil when removing premix from the pouch.
Prepared Agar Plates
Store prepared plates sealed and upside down after the agar has fully set.
Refrigeration can help extend storage life.
Keep prepared plates away from freezing temperatures and excessive temperature changes.
Allow refrigerated plates to return closer to room temperature before use.
Condensation
Some condensation is normal, especially in the top plates of a freshly poured stack.
To help reduce condensation:
- Allow the agar to cool before pouring
- Avoid pouring while the agar is extremely hot
- Let the plates cool in a clean area
- Store fully set plates upside down
- Avoid rapid temperature changes
Do not open the plates simply to remove condensation, as this can introduce contamination.
Troubleshooting
The agar did not set
Confirm that the correct ratio was used:
20 g premix per 500 mL water
Using too much water may prevent the agar from setting properly.
The agar began solidifying before pouring
The mixture cooled too much before it was poured.
Gently reheat the bottle using a hot water bath until the agar becomes liquid again. Do not place a sealed bottle in a microwave.
The plates have excessive condensation
The agar may have been poured too hot, or the plates may have cooled too quickly.
Allow the agar to cool to approximately 120°F to 130°F before pouring.
The agar has bubbles
Swirl the bottle gently instead of shaking it.
Pour slowly and evenly.
The agar color looks uneven
Swirl the bottle gently before pouring to evenly distribute the ingredients.
Avoid vigorous shaking, which can create bubbles.
Growth appeared before inoculation
The plate may have been contaminated during pouring, cooling, or storage.
Discard contaminated plates and review your sterile technique and workspace cleanliness.
Safety Information
Agar remains extremely hot after sterilization and can cause serious burns.
Always use heat-resistant gloves when handling hot bottles or media.
Never fully tighten a bottle cap during pressure sterilization.
Never open a pressure cooker or autoclave while it is pressurized.
Do not use cracked, damaged, or non-heat-resistant containers.
This product is intended for mushroom cultivation, laboratory, educational, and research use.
Ready to Start Growing?
Use our Agar Premix with your favorite mushroom culture or pair it with our other cultivation supplies.
[Shop Agar Premix]
[Shop Agar Plates]
[View Mushroom Grow Guides]
Need Help?
Questions about mixing, pouring, or using your agar?
Contact Sierra High Mushrooms at:
Sierra High Mushrooms
A small family business at the foot of the Sierra Nevada